Superchargers can be used to significantly increase the horsepower (“HP”) and torque produced by an internal combustion engine through forced induction which boosts the mass flow rate of air to support combustion over what would normally be available through conventional or natural aspiration. Superchargers can take a variety of forms including positive displacement (e.g., roots-type and screw-type) and dynamic compressors (e.g., centrifugal), but all types are essentially pumps which need to be driven to produce the desired increase in power output. The amount of engine power consumed by the supercharger, termed “parasitic loss” can be significant especially in high boost applications.
Superchargers can be driven by a variety of means but are typically driven by the supercharged engine itself through a mechanical coupling such as a belt, gear, shaft, or chain. For example, the commonly-utilized and popular centrifugal supercharger is often belt driven, particularly in after-market applications where relatively straightforward modifications to the existing engine belt drive system can be made to accommodate the supercharger installation. For example, the serpentine belt drive used to provide input power from the crankshaft pulley to existing engine accessories such as the water pump, air conditioning compressor, alternator, power steering pump, etc., can typically be adapted to enable a belt to be routed to the supercharger input pulley.
Such belt drive adaptations can provide satisfactory performance results in some cases while minimizing the engineering expense and installation complexity that would be expected to accompany other drive systems. However, sharing the same belt between the supercharger and other engine accessories can be problematic in high boost/power applications where the parasitic supercharger loss can be high. In such cases, the engine may need to impart a large amount of power through the belt drive, for example 50 to 100 HP or more, which is far in excess of the loads the system was originally designed to bear. For example, the OEM (Original Equipment Manufacturer) components such as accessory brackets may emerge as a point of failure and present such problems as deflection under load that causes belt misalignment which reduces drive efficiency and can increase bearing load, or result in outright catastrophic failure in some cases. While replacement accessory brackets can be installed in an attempt to address this issue, such solutions can add expense and present additional installation complexity. The effectiveness of the solution can also be limited in many applications because space is typically at a premium due to the tight packaging of most modern engines.
Another problem with sharing the belt drive between the supercharger and engine accessories is posed by running the long serpentine belts that are typically necessary. Long belt paths tend to exacerbate problems with pulley alignment among the driven components and the long spans can also generate complex non-linear belt motions including vibration and resonance that can require additional components such as idlers and tensioners to be engineered and installed. Such components not only can add expense and installation complexity but may be restricted in their application in some cases because of the limited available space.